Inconsistent use of bytes length/encodings?

`createSalt` generates `keyLength` bytes and then transform it in a base64 string. This string is passed to `pbkdf2` as salt, but pbkdf2 treats strings as utf8, so the given salt is not the same random sequence of bytes generated early.
Can be assumed that the salt is still random even if has been expanded by the inconsistent use of the encodings? Are there any security implications? Usually in cryptography when you introduce some fixed points you open yourself to some kind of attacks.